Depth of Field refers to the range of appearance of image sharpness in focusing by the image sensing device. In the optical, especially the video or photography, the depth of field is a description of distance for the object having sharp focus in the space. General lens can only focus the light to a fixed distance and away from this distance the sharpness is gradual decrease, but the unsharpness is imperceptible under certain distance, i.e. so called the depth of field. To eliminate the limitations of the depth of field, the image sensing component requires a variable focus function.
In the present LCD display panel manufacturing industry, the image sensing module and display panel were combined to form a multi-function display to achieve both the purpose of image scanning and displaying. The image scanning functions such as computer cameras and computer eyes. The multi-function display used as a video input devices are widely used in video conferencing, telemedicine, real-time monitoring and so on. In recent years, the network speed continuously increasing accompanied with the development of Internet technology and the techniques of the component using in sensing the object into the image is mature and widely used in the manufacture of the multi-function display, therefore the two ends can communicate with each other with image, video, voice conversation and communication through the video input devices in the network. Furthermore, the multi-function display plays an increasingly important role in people's lives and work since it can also be used for processing the current various popular digital imaging, audio and video. However, the image sensing module used in the multi-function display has a fixed focal length range, so its imaging sharpness is limited by the depth of field and with poor performance.
In addition, the traditional glass or plastic lens is only a single focal length, and no variable focusing function. It would be desirable to provide zoom lenses with variable focusing as the name implies more than two traditional lens combination and employs a voice coil motor (VCM) or piezoelectric actuator to change the relative distances between the zoom lenses to obtain variation and magnification of focusing. However, for the traditional autofocus zoom lenses module the volume of the voice coil motor been a trouble in oversize and resulting the difficulties in application.